Overview of the Integumentary System

Feb 5, 2025

Dr. Young's Anatomy Class: Chapter 5 - Integumentary System

Overview

  • "Integumentary" refers to the skin.
  • Skin is composed of several layers and structures:
    • Epidermis: Top layer, avascular, relies on diffusion from lower layers.
    • Dermis: Middle layer, contains blood vessels and sensory receptors.
    • Hypodermis: Not part of the skin, fatty layer with large blood vessels.
  • Accessory structures: hair, sweat glands, oil glands, nails, sensory receptors.

Epidermis

  • Composed of several layers:
    • Stratum Basale: Base layer, contains germ/stem cells, one cell thick.
    • Stratum Spinosum: Keratinocytes begin to dehydrate, appear spiny.
    • Stratum Granulosum: Active keratin production, cells dehydrate more.
    • Stratum Lucidum: Found only in thick skin, a clear layer.
    • Stratum Corneum: Top layer of dead keratinocytes, waterproof.
  • Contains other cells:
    • Dendritic Cells (Langerhans cells): Act as immune cells.
    • Merkel Cells: Light touch receptors.
    • Melanocytes: Produce melanin, skin color determined by activity level.

Dermis

  • Papillary Layer: Thinner layer, loose connective tissue, contains dermal papillae.
    • Consists of small capillaries and Meissner’s corpuscles (light touch receptors).
  • Reticular Layer: Dense irregular connective tissue.
    • Contains laminated corpuscles (pressure/vibration receptors).

Skin Functions

  • Protection: Barrier against external damage, immune function.
  • Sensation: Contains various receptors for touch, pressure, temperature.
  • Thermoregulation: Sweat glands help cool body by sweat evaporation.

Thick Skin vs. Thin Skin

  • Thick Skin: Located on palms and soles, has more stratum corneum layers.
  • Thin Skin: Found on areas like back, has fewer stratum corneum layers.
  • Calluses are thickened skin areas due to excessive use.

Skin Cancer

  • Basal Cell Carcinoma: Most common, originates from stratum basale, rarely metastasizes.
    • Appears as red nodules with a crater-like appearance.
  • Squamous Cell Carcinoma: Second most common, scaly plaques that bleed, can metastasize.
  • Melanoma: Fast-growing, originates from melanocytes, highly metastatic.
    • ABCDE Rule for Detection: Asymmetry, Border irregularity, Color variation, Diameter > 6mm, Evolving changes.

Accessory Structures

  • Hair: Includes dermal root and hair shaft; linked to erector pili muscles.
  • Nails: Made of hard keratin, provide dorsal protection.
  • Glands: Includes sweat and sebaceous (oil) glands; sebum is the oil produced.

Skin Features

  • Fingerprints: Created by dermal and epidermal ridge interaction.
  • Cleavage Lines: Natural lines in skin, important for surgical incisions to reduce scarring.

These notes summarize the key points discussed in Dr. Young's lecture on the integumentary system, focusing on the structure, function, and various conditions related to the skin.

Full transcript